The present invention relates generally to welding-type systems and welding-type power sources and, more particularly, to a controller for welding-type systems configured to control a welding-type system to operate according to a variable maximum duty cycle based on a current temperature, in, about, or of the welding-type system to reduce the likelihood of inducing a thermal shutdown of the welding-type system. Furthermore, since the present invention has a temperature feedback input, allows the variable maximum duty cycle to exceed a rated duty cycle under appropriate operating conditions thereby enabling the welding-type system to operate above the rated duty cycle.
There are numerous variations of welding-type systems. Each variation of welding-type system is typically designed to operate according to one or more specific welding-type processes. For example, some common welding-type systems are designed to operate according to a Metal Inert Gas (MIG) welding-type process, formerly known as Gas Metal Arc Welding-type (GMAW) process, a Tungsten Inert Gas (TIG) welding-type process, a Shielded Metal Arc Welding-type (SMAW) process, a stud welding process, a plasma-cutting process, induction heating process, or other welding-type processes.
All welders and welding-type processes employ components that generate heat during operation. For example, stud welding processes are designed to supply high current for short periods. That is, stud welding is a welding process that utilizes a localized burst of current between a metallic fastener and a metallic work piece. In most instances, although not required, the fastener and the work piece have the same material properties. The fasteners are held and welded in place through the use of an electromechanical device known as a stud gun. A stud welder power source generates and discharges a high current output in a short period of time that serves to weld the stud to the workpiece.
The high power generation and discharge associated with welding processes result in a high level of stress on the components of the welder. As such, some welding machines typically have relatively low duty cycles. Generally, the welder is designed to have a rated maximum duty cycle based on an assumed maximum operating temperature. That is, welders are designed to operate at a maximum duty cycle corresponding to temperature tolerance of the welder. To ensure that the welder operates within this temperature tolerance under all operational conditions, the maximum duty cycle is typically fixed so that the welder remains below the temperature tolerance under relatively high temperature operating conditions. For example, stud welders are typically physically limited by a fixed time lapse between welds that is based on a “worse-case” operating environment where the stud welder is operated under the harshest of operating conditions that include a maximum operating temperature.
In this case, regardless of operating conditions, the duty cycle of the stud welder is limited by a maximum duty cycle when, in fact, it may not be operating at the maximum temperature tolerance of the power supply. Therefore, although operating temperatures would allow performing at a higher duty cycle, the stud welder is precluded from operating above the rated duty cycle. That is, under some operating conditions, such as when the operating temperature is below the “maximum,” the power supply may be capable of operating above the “worst-case” rated duty cycle, but is restricted from exceeding the “worst-case” rated duty cycle.
Although most welders employ a hard duty cycle limit to keep the operating temperature below the temperature tolerance of the power supply, the temperature, in, about, or of the power supply may still surpass the maximum temperature tolerance of the welder. Accordingly, welders often utilize a thermal shutdown mode whereby, if the operational temperature of the welder approaches or surpasses the maximum temperature tolerance, the welder enters a thermal shutdown and ceases operation. Specifically, should the operational temperature of the welder surpass the maximum temperature tolerance, the welder power source enters a “standby” or thermal shutdown mode that allows the welder to cool.
While this thermal shutdown mode protects the welder from possible damage due to overheating, it also interrupts the welding process. Accordingly, should the power source enter the thermal shutdown mode, the operation of welder idled. This break in the workflow can be particularly undesirable in settings where there may be interdependence between various procedures. In some cases, a significant break in the welding process may require corresponding delays in subsequent steps in the workflow.
Additionally, a break in the workflow necessitated by the welder entering a thermal shutdown mode may encourage an operator to leave the welder workstation while the welder cools. As such, the operator may not be present to resume the welding process precisely when the welder returns from the thermal shutdown mode. As a result, the break in the workflow caused by the welder entering the thermal shutdown mode may be unnecessarily extended. As a result, additional delays are incurred in the workflow and productivity is further decreased.
It would therefore be desirable to design a system that may be controlled to operate above a maximum rated duty cycle of the system based upon actual operational conditions, such as temperature. Furthermore, it would be desirable to have a welding system with a variable duty cycle and a controller configured to dynamically adjust the variable duty cycle to reduce the likelihood of the welding system entering a thermal shutdown.